[c-nsp] How to troubleshoot input queue drop continuously on Cisco7600?

[Peter Rathlev]

On Mon, 2014-10-20 at 17:00 +0700, PlaWanSai RMUTT CPE IX wrote:
> k1#sho int te1/4
> 
>   Last clearing of "show interface" counters 00:12:35
> 
>   Input queue: 0/200/69739/69739 (size/max/drops/flushes); Total output
> drops: 0

On this platform those drops could be for traffic forwarded to the CPU.
What does the interface configuration look like? Is it a L3 interface
("no switchport"), or is it a L2 interface? If the latter, and you have
SVIs (VLAN interfaces) for some of the VLANs it carries, look for drops
on those SVIs.

If they are "microburst" drops on L3-interfaces then you can possibly
mitigate it using "hold-queue <N> in" on the L3-interfaces (SVIs or the
"no switchport" interface itself). This is a trade-off; don't use a too
high setting for input-queue or you will get other problems.

You could use a SPAN session to look at what traffic might cause this.
The SPAN replication is before traffic is forwarded to the CPU so you
should be able to see floods.

>   1    4  CEF720 4 port 10-Gigabit Ethernet      WS-X6704-10GE

This card has rather small queues so it might simply be microbursts. In
that case you might have to find a port on another card.

For general info about input queue drops this is a good read:

http://www.cisco.com/c/en/us/support/docs/routers/10000-series-routers/6343-queue-drops.html

-- 
Peter